Flight control system



Aug. 18, 1953 J. M. SLATERl ET AL FLIGHT CONTROL. SYSTEM 3 Sheeis-Sheet1 Filed March l5, 1947 Aug. 18, 1953 1 M, SLATER HAL 2,649,264

FLIGHT CONTROL SYSTEM Filed larch 15, 1947 3 Sheets-Sheet 2 INVENTOR Sdof/N M. SLA TER W/QL TER WR/GL E Y TTORNEY Aug. 18, 1953 J. M. sLArERETAL 2,649,264

FLIGHT CONTROL SYSTEM Filed latch 15, 1947 3 Sheets-Sheet 3 5LB/Aron?INVENTORS dof/N MJSLAT R WHL 75H wR/GLEY Paterxted'l Aug. 1,8,

UNITED STATES PATENT om@ s FLIGHT CONTROL SYSTEM" John M. slater, Gardencity, N. Y., ,anavvauer Wrigley, Wollaston, Mass.,l assgnors to' ",1l`1e Sperry Corporation; a corporation ofl Delaware' Application March 15,1947; SerialjN-ol 'TSBE 34 Claims. (Cl. 244-77) This invention relatesto automaticiglit: con; trol systems fer dirigible craft and missilesyand, in particular, relates to flight control apparatus" forautomatically producing control moments for' entering and maintaining acraft or a missile a predetermined flight pattern,.be that pattern onefor' producing straight and level' iiight, banked turns, or complexmaneuvers such as steeply climbing turns. V

More particularly, the primary object'` of' the: instant invention is toprovide an autopilot which is primarily based on torqued gyroso'r rategyros which move with the craft or missile" in order toiacilitate theexecution of acrobatic' maneuvers, While'simultaneously preserving ati'titude references with respect to theV earth (a`t"` titude herein beingintended to include heading references as Well as the usual levelindicating references). Conventional auto'pi'lo'ts basedion gyroverticals and directionaijgyros are adequate 'for ordinary civil andmilitary maneuvers", but it is very difcult to make these pilots' con;trol very steep turns, or spiral turns. On-the" other hand, while flightcontrol systernsemployr' ing torqued gyros, or rate gyrosaiiord uniformcontrol action in all attitudes, there isno sim-'I ple or obvious Way topreserve earth references' durin'I maneuvers. The presentinvention'pro#' vides a system combining the virtues of each of theaforementioned types of auto pilots; Specil 3Q' cally, aircraftreferenced gyros or other angular movement responsive devices ofinertial 'type (see below) are herein providedior obtaining shortIperiod control, While earth referenced gyros serve as monitors, therebyproviding long period con; trol and furthermore means are provided'whereby proper signals are supplied to aircraft gy'r'os to makemaneuvers'with respect to earth axes.`

Angular velocities (and accelerations) about aircraft axes are not thesame as those about the earth referenced axes except in the one specialcase of level flight. For example, ina climb'- ing turn, craft headingchanges, and craft angle of bank and craft'angleof elevation remainconstant, but angular velocities Occur about all three primary craftaxes.

It is a further object oi the instant invention to provide a system forsupplying proper signals to craft control-moment producing mechanismsfor making turns or other maneuvers wherein said proper signals aredependent upon measures of angular velocitiesV that must exist abouteach craft axis if said predetermined ma neuver is to be evolved.

The equations that follow set forth the rela- 2 tionsv thatAexistbetvveen an" earth-referred coordinate system and a craft referredcoordinate system, where, in the case oi `the earth-referred coordinatesystem, three'pr'iniary axes are denoted as Xe, Ye and Ze, (the Xe axisbeing northsouth', thev Yeaxis beingY eastLWest and the Zeaxis',extending'doivnwardly), and Where, in the craftaxes (longitudinal,transverse andperpen- I dicular) are referred'tofasXetYa, and Za. Furl"ther, heading is'delnedas" the'a'ngle between the Xe axisv andthe'projec'tion o'f Xe on a'horiaon' tal plane, and'is denot'edbyqiRate' o1 change of`heading,` or rate of turn -is` denoted by gb. An?

,gie of bank is clenedY asi'the angle between the be"lugatr'clelatVinstant as involving merely a rotation abouttsomejaxis anda translationalong some direction. n,In most vcases the axis about which rotationtakes place is a vertical one, that iis, most' turi'sIvv/"hether `vlevel-lor climbing, are made about a-vertical' axis. Furthermore,ordinarily"V ,the only t'ra'r'i'slationf that is desirable is thatalongtheinstantanousf Hight path, that-is, side-slip andaretoloeprevented.' Thus one object of the inventionis to cause angularvelocity components about the three aircraft axes which are suchasto'causea predetermined angular"velocityto`*takeplaee about a verticalaxis. This is achieved'by acor'p'uting and control system which, oniactuation, causes components of angular velocityVA Wxa, Wya, Wea, whichcorrespond to a given rotation-rate 'a-bouta vertical axis, thesecomponents being-dened by the ex pressions erm-nr) W'hereV=truefa`irspeed, and giaccelerationjof gravity. A mregeneralexpres'sion-to include climbing turns is The instant inventionadditionally recognizes that while in some instances it may be desirableto produce a computed craft bank angle in accordance with apredetermined craft rate of turn, in some other instances it may bedesirable to produce a computed craft rate of turn in accordance with apredetermined craft bank angle. For example, in bombing and certainother military maneuvers it is desirable to predetermine rate of turn,and let the 'bank angle be a dependent variable, whereas in ordinarycivil flying, the converse arrangement is preferable as it avoids thepossibility of an excessively great bank angle inadvertently being setin at high airspeeds. The equation for computing a craft rate of turn(qb) for a predetermined craft bank angle (B) would be Heretofore,systems have been provided to include rate sensitive gyros positioned incertain craft axes coupled with means for biasing these gyros inaccordance with functions of rate of turn and craft bank angle. Forexample, Thiry, in U. S. Patent 2,190,390, proposes such a systern.However, these systemsI provide only an approximate solution of thecraft angular rates and consideration of the angular rates involved inclimbing or gliding turns is entirely overlooked. At best, these systemsafford only an approximate solution even in level or constant altitudeterms. The approximation and limitations of the systems known to the arthave been removed by the features of the inst-ant invention and a systemfor supplying proper signals to the craft for achieving complexmaneuvers is herein provided which is completely general for steeplybanked turns at constant altitude, or for steep climbing or descendingturns.

The invention also relates to the novel features or principles of theinstrumentalities described herein, whether or not such are used for thestated objects, or in the stated elds or combinations.

Other objects and advantages will become apparent from thespecification, taken in connection with the accompanying drawings,wherein Fig. 1 is a schematic illustration of a ilight control systemembodying features of the instant invention;

Fig. 2 is a schematic illustration of a computer mechanism for thesystem of Fig. 1;

Fig. 3 is a schematic illustration of an alternative flight controlsystem embodying features of the instant invention;

Fig. 4 is a schematic illustration of a computer mechanism for thesystem of Fig. 3; and

Fig. 5 illustrates schematically, an alternative inertial device for thesystems set forth in Figs. 1 and 3.

Referring now to the drawings, Fig. 1 sets forth an embodiment of theinstant invention wherein rate of turn is predetermined and controlmoments are applied to appropriate craft control devices in accordancewith the predetermined rate of turn. In Fig. 1, the control knob II isprovided with a signal generator I2 including the winding I3 which isoperatively associated to be turned by the knob II and the winding I 4which is relatively xed Within the generator I2. Coil I3 is energized bythe source I5, and the coils I3 and I are arranged so that for variouspositions the knob II, each reilecting a predetermined rate of turn, asignal of phase and amplitude corresponding to the sense and magnitudeof displacement of knob II will appear between points I6 and il of thesignal generator l2. The output from the signal generator I2 thuslyappearing at points I6 and Il is thereupon supplied as an input of thecomputer I8. Computer I 8 will be more fully described in relation tothe disclosure of Fig. 2. For the present computer i8 may be consideredto have an output in accordance with the equawhere 0B=computed angle ofbank for a predetermined rate of turn up); V=craft airspeed; 0E=craftangle of elevation or pitch angle; and gzacceleration of gravity. Aswill be later described in detail, the signal appearing between points2I and 22, or the output of computer I3, will be a signal dependent uponthe computed bank angle 0 13 for the given or predetermined rate of turnqa as set in at knob II. The vertical gyro 23 is provided to establish areference responsive to actual craft bank angle (0B) and is mounted inthe craft with a pick-01T 25 which may be of the selsyn type. The signalproduced in lines 25 and 26 'by the pick-off 24 will be in proportion tothe actual craft bank angle (0B). If the computed craft bank angle (HB)differs from the actual craft bank angle (0B) a signal will appearacross the lines 2l and 28 which will be dependent upon the differencebetween the computed and the actual craft bank angle.

As has been previously described herein, a signal that is responsive tothe preedtermined rate of turn, as set in the knob I I, is producedbetween the points I and Il. However, there are two further factors thataffect craft rate of turn which must be considered in any completesystem. These factors arise, firstly, in the event the craftinadvertently undergoes a slip or a skid condition, and secondly, in theevent there occurs a residual heading error after the craft hascompleted a turn. The apparatus, in this embodiment, for solving theproblems that arise from these two factors will be considered in theabove order. In theory no side-slip will occur because computer i8,being more properly referred to as a coordinating computer, thoughhereinafter referred to as a computer, keeps the bank angle adjusted tosatisfy the dynamical considerations expressed in the equation @Bean-(LHE) Should any side-slip occur, by reason of an error in air speed data,for example, it is removed by means of a slip and skid detector, in thisinstance the pendulum 3i, which is provided with a signal generator 32,and is energized by the source I5. rlhe signal generator 32 may be ofthe selsyn, or other appropriate well-known type, and has an outputtransmitted by lines 33 and E34 which is proportional to slip or skidand is applied in conjunction with the output from the computer I8 in asense which will increase or decrease the angle of bank signal appearingacross the points 2I and 22 thereby causing the skid or slip to beovercome. A signal isolating device which for the purpose ofthe instantapplication may be represented to be the amplifier v3l), which maycomprise a standard form of amplifier with the signal from the signalgenerator 32 being applied to the grid of a vacuum tube (not shown) andthe output taken from the cathode circuit and applied to the points 2|,22 of the coordinating computer i8, thereby servingl to permit thetransmission of signals through amplifier in only one direction. Thussignals emanating from the signal generator 32 are transmitted throughthe amplifier 3G to aifect or modify the computer output but signalsfrom the computer output are prevented from affecting the signalgenerator 32, by virtue of the isolating quality of the amplirfier 3G.

While there are other instances in the several figures of the instantapplication wherein similar signal isolators could be advantageouslyemployed, these so-called isolators have not been shown as they arewell-known in the art and to include them would unneecssarily complicatethe illustrations.

A stabilized azimuth reference is provided conveniently, in the form ofa saturation compass or flux valve 3l mounted on the gyro vertical 23.The rlux valve 3l is energized from a source l5 and is connected in aknown manner to a selsyn 33 the output of which is ampliiied at lli. The

output can be applied by switch 42 either to the turn control signalchannel iii-i? or to a followup motor 43 which drives a differentialselsyn :le in a sense to keep the output of selsyn 38 zero as describedbelow. rlhusly, during a turn on rotation of the knob il, cam l5 fixedto rotate with knob i willA cause the arm lieto be dise placed from thedetent 4i of the cam 35, closing Contact point and energizng lines 5iand 52 to the battery 523, thereby energizing the coil 54 of thesolenoid 55 causing the switch l2 to be moved (to the left on thediagram) thereby to transmit the output from the amplifier 'lli toenergize the motor e3. The motor 43 rotates the selsyn M. at a rateequal to the rate of turn of the craft, so that when the turn is stoppedthe craft will be controlled on its new heading. In straight flight, anyresidual heading error results in a iiui; valve error signal whichcauses the airplane to turn until the error is eliminated by reason ofthe error signal being transmitted along the lines E5 and 5l to theinput of the computer it, or, more particularly, any residual headingerror will be productive of a signal across the points l and il andthence be transmitted as an input to the computer i8. Thereupon a signalserving to effect a heading change is created and this signal willpersist until such time as the actual craft heading is in agreement withthe predetermined heading. It is in this manner that the second factorfor modifying the predetermined craft rate of turn is created within thesystem.

The vertical gyro 23 is also provided with sig-I nal generators forcomputing proper signals for transmission to the craft surface controlmechanisms in accordance with the expressions as hereinbefore set forth.The signal generators, as will be explained, are in general required toproduce outputs corresponding to the sine or cosine of the angle ofdisplacement of the rotor and stator, as the case may be, andthey canconveniently take the form of known single phase selsyn synchros which,when operated away from the position of full coupling have acosinusoidal output function and when operated away from" thepositionofzero coupling `have asinusoidal output function.

Located on the pitch axis of gyro 23 isa sine selsyn 58. Byenergizngzthe selsynwith a signal that is proportional to predeterminedcraft rate of turn (fp), vwhichis transmitted along the lines 3.5 and3B, an output will be produced that is proportional to the productorcraft rate of turn and sine of the angle of kelevation (e sin rpc). Thissignal (e sin ce) is combined with a second signal which is proportionalto the difference between actual craft bank `angle and computed craftbank angle (BB) and the combination applied as'an input to an angularmovement responsive inertial device located von a primary craft axis, orin this instance, located on the craft roll axis. The angular craftmovementresponsiveinertial devices herein provided in each of theprimary craft axesmay be any of several well known types. The instantembodimentprovides for torqued gyros for .yieldingr craft controlsignals, but other similar devices suchas rate gyros, the vibratoryangular-velocityresponsive devices of Lyman Reissue 22,409 or angularaccelerometers, would be satisfactory. inasmuch as the exact nature ofthe signal emanating from'the inertial device will depend upon the typeof device employed (i. e. displacement, rate or acceleration-sensitivemeans), the signal that is eventually supplied to the servomotors forthe craft control surfaces will depend upon the amplifying circuitinterconnecting the output from-the inertial devices with theservomotor. These control signals may contain cornponents of rate,displacement or derivatives thereof the selection being more or lessdependent upon the particular application in which the system isemployed, and means for obtaining signal components responsive to rate,displacement, etc. are wellkncwn in the art.

The signal proportional to sin 6E) and the signal proportional to(9B-WB) are, in the preferred embodiment, supplied to the two separateprecession torquers `Eil and 6| respectively, lon cated on the gyro 62.The remaining instances wherein two orl more independent signalsourcesare indicated as supplying signals to a single precession torquer, wouldalso preferably provide a separate torquer for each signal (or othermeans for preventing intermixing of independent sighals), but forreasons of simplicity, hereinafter only the single torquer is shown. Thegyro S2, and the several other similar inertial devices appearing in thedrawings are preferably provided with pick-off and torquer means (notshown) for maintaining the spin axisat right angles to the plane of thegimbal member, in a known manner. `In response to the signals applied tothe precession torquers El and `6|' gyro 62 will precess at a ratepropotional to the sum of those signals. Pick-off- 63 is p-rovided toproduce a signal output proportional to the angular displacement of gyro52 relative to the craft whereupon this last-mentioned signal istransmitted to appropriate aileron controls including amplifier means ina manner Vsimilar to that shown in Fig. 3.

The vertical gyro 23 is additionally provided, along its roll axis, withthe cosine selsyn S4 and the sine selsyn 55 for computing the quantityqb cos 0B and the quantity @sin 0B in the manner illustrated. Thequantity qa cos 0B is transmitted along the lnesandxlto a secondv cosineselsyn `681y locatedfon .thegpitch axis ofi the'verticalfgyro 23. Theoutput from this second cosine selsyn 68 is proportional to (qs cos 0Bcos 0E), and this output is transmitted along the lines and 12 to theprecession torquer 'I3 located on the torqued gyrov 'I4 which in thisinstance is used for supplying signals through the selsyn pick-o 'l5 torudder control means. The output from the sine selsyn 65 is conducted bylines 'i6 and TI to a cosine selsyn 18 located on the pitch axis of thevertical gyro 23 and is productive of an output proportional to (qs sinB cos 0E) which signal will be transmitted along the lines 8| and `82 tothe precession torquer 83 located on the torqued gyro 84 thereby causingthe selsyn pickoff 85 to produce a control signal which is transmittedto the elevator control means.

Gyros I4 and 84 are also provided with pickoff and torque means, notshown, for maintaining the spin axis at right angles to the plane of thegimbal member, in a, known manner.

In order to provide means for effecting climbing turns, or other complexmaneuvers, the signal generator I3 is pivoted by means of the mountingrod B in a manner to permit movement of the control knob in accordancewith predetermined angles of elevation. As the control knob II is movedbackwardly or forwardly, selsyn 81, `provided on the mounting rod 86produces a signal in the lines 88 which signal will reflect the extentof motion of the control knob II, or more specifically, which signalwill be dependent upon the predetermined angle of elevation (6E).

Operatively associated with the selsyn Si, by means of the transmissionline 88, is a selsyn 9| located on the pitch axis of the vertical gyro23. In order that the surface control devices hereinbefore mentioned besupplied the correct signals for producing craft control moments inaccordance with -a predetermined angle of elevation, signalsproportional to the predetermined 0E are supplied along the lines 92 and93 to a cosine selsyn 94, and also to a sine selsyn 95, located on theroll axis of the vertical gyro 23. In this manner two output signals aregenerated; one signal appearing between the lines 96 and 9'! isproportional to the quantity 0E cos 0B and this output is transmitted tothe elevator control device in combination with the signal (o sin 6B cos6E) heretofore mentioned; and in a similar fashion, the second outputoriginates in the sine selsyn 95, and appears across the transmissionlines 98 and 99, and is proportional to the quantity 0E sin 6B. Thissecond signal is supplied to the rudder control device in cooperationwith other signals (o cos 6B cos 6E) also heretofore mentioned.

From the description thus far, it can be seen, in the system provided,that the craft may be controlled in straight and level iiight lby meansof the torqued gyros that are provided on each of the three craft axes;or, if desired, `a constant altitude rate of turn may be set in by meansof the knob I I whereupon a computed angle of bank will -be maintainedby the craft in accordance with the equations hereinbefore mentioned;or, if desired, a spiral turn may be evolved 'by presetting anappropriate angle of elevation in addition to the predetermined rate ofturn, whereupon the proper signals will be produced by the devicesmentioned and these signals will be productive of proper control signalsfor maintaining the craft in any of these predetermined maneuvers.

In Fig. 2, the details of the apparatus included in the computer I8 thatappears in Fig. 1 are set forth. 'I'he object of this computer' |"8 isto rel" ceive a signal proportional to the predetermined craft rate ofturn (qb) and to be capable of producing, as an output, a signal that isproportional to the bank angle that is correct, for that particularpredetermined rate of turn. Thusly, the computed craft lbank angle wouldbe in accordance with the equation;

Fan-(L @5S a) Specifically, the apparatus of the computer includes atrue air speed meter which is coupled by means of the shaft I I2 to alinear selsyn ||3 in a manner whereby the shaft |I2 is made to turnthrough an angle proportional to the craft velocity. An alternatingcurrent source ||4 serves to energize the linear selsyn ||3, and theoutput from the selsyn, appearing across the lines ||5 and IIB, isproportional to the craft velocity. A turn control knob which may be thesame turn control kno-b that was provided in the system of Fig. 1, andhence bearing the same number, is operatively associated With a linearselsyn II'I. Upon rotation of the knob I I, a signal output from theselsyn Ill will be produced across Ilines |I8 and I|9 and that signaloutput will be in proportion to the product of the predetermined craftrate of turn, (fp) as set in the knob Il, and the craft velocity, (V)`as measured by the meter III. In Fig. 2, vertical gyro 23 isillustrated as provided with a cosine selsyn |22 positioned on its pitchaxis. The output lfrom the cosine selsyn |22 by virtue of thearrangement illustrated is therefore proportional to the product of thecraft rate of turn, craft velocity and the cosine of the craft angle ofelevation (V cos 0E) This output appears across transmission lines |23and |24 and is transmitted thereby to a device that will produce anangular displacement that is proportional to the angle whose tangent isequal to that output.

More specifically, this output is applied across the wiper |25 and thefield Winding E2? of the motor |28. The wipper |25 is positionable onthe auto-transformer |26 by means of the motor |28 which is energized bya source of alternating current H4. The alternating current source ||4is applied in series with the adjusting resistor I 29 to the eld windingI3| of the motor |28 and also to points |32 and |33 of theauto-transformer |26. In this manner the signal appearing across thelines |23 and |24 will cause the motor |28 to turn the shaft |34 throughthe gears |35 and |36 in an amount proportional to the signal suppliedthereto. Further, the angular displacement of the wiper |25 from thevertical Will be proportional to the angle whose tangent is proportionalto the signal applied to the eld Winding I2'I, or more specifically inthis instance, to the angle whose tangent is equal to the product rpVcos 0E. Directly associated with the shaft |34 is the selsyn |31, whichis rotatable with the shaft I3l and the wiper |25. The selsyn |3'I isenergized with-an alternating current source Ils and is rotated from avertical position to an angle dependent on the value of the signal inthe lines I 38 and |39, and is therefore productive of an angulardisplacement proportional to the angle of bank as computed in theabove-described manner. The vertical gyro 23 is also provided with -aselsyn pick-ofi I4I which is located on the craft rollaxis. Analternating current source Illi is provided for the selsyn |4| whichthereby is 9 productive oianfoutputialong .lines i 43 and; |44thatisproportional to the :actual #craft Ybank angle. Byconnectingthe'actual. craft bankaangle signal `in opposition tothe computed craftbank angle signal in the manner illustrated; anoutput signal appearingacross the points idfiiand |35 will be produced `which will reectinstantaneous deviation of the actual value from thepomputed value.'This :quantity .'appearin0r Lacross i points trols through the lines 2Land .221,that appearlin Fig. :1,y whereupon control moments are appliedto the craft vuntillsuch time as thei signal Vinnlines |39 andMii-becomeszero.

.11n the embodimentof the'iinvention shownziu Fig. l, the`aircraft-.iscontrolled'jointlyby the aircraft-.axis gyros 52, 'id-'fandandftlie'a-earth reference gyro '23. .In :some kcases it 'may "bedesirable tocause the 4short period controltto :be

performed `practically 'entirely by Ythe aircraft :The 1 apparatusillustrated as connecting the torquer-fl .of gyro162with:thesignalireceived from the earth referencegyro23^and`thecoordinating computer i8, indicates how this may be accomplished'in the7caseof the aileron control system. :Similar: apparatus .may Vbe addedto the rudder and *elevatorY control systems though-not shown herein.AvA potentiometerl iti) yisfarranged in-leadsZ', 28 inta: manner thatwhen' the'wiper HH 'is-in a downwardjposition.the sensitivitytofthesignal channel is reducedto a lowivalue, and Vwhen the wiper-i151is'in'an upward position the sensitivity is at its'full value. The Wiper-is :driven through stepdown gearing` |62 by a -mctor- 53' takingsignals from leads2`| `andfZS beyond the potentiometer. .The Vmotoriebiased by-a battery |54 so that the wiper itl .is normally slowlymovedtoward'a down'positionand `in normal-steady -state condition it restsinthat down position. The signalk from leads '2l and '23 is Yarfipliiedand 'rectied inthe Vamplifier .|55 and ap-plied tothe motor i53- in4a-isense-tornove the lwiper up (whatever the. senserof thefsignal fromleads 27.*and 23) `and thereby toincrease the sensitivity of the channelon occurrenceof suchsignal. -Asolenoid and: plunger Hi8v isconnectedthrough vleads lii'and i0 to the leads 5|, 52 (the -symbolsA-.Aindicatingr the connecting point in the diagram) `sothat when the turnknob is moved fromfzerofthe'wiperfidi ispulled .upwardly. In oper-ationin normal straight and levelfiight the-wiper is down so that-the signalfrom pickup 2.1i is greatly attenuated before reaching torquer-SI..-Short-period control ofrthelaircraft. is practically 'entirely by thegyro 52. lillisturbances due to Vgusts;momentary changes vof center ofgravity, etc. are corrected by this gyro but if a persistent drift ofrthe gyro 62 occurs, then a persistent .error signal :at itt, le?gradually causes wiper i t! to rise, increasing the sensitivity ofsignalchannel v2 and :iSv-so-that .theerror signal frompick-oif can getthrough to`A torque gyro -62 in' a sense to restore attitude. 'Tornake aturn, theknob llisl moved from `Zero position. This energizes linesitiiand 59 untilfthe condenser lt ischarged;butinitially-oausing*solenoid'i'to raise the wiper ||l| `to yafull 'sensitivity' position so that the airplane banks. tothe computedbank angle andzis'then stopped' banking by the-signal from the.pick-offizii. :Assuming that the :computed-bank angle'iscorrect, thesignal'in leads f2l and 222 will shortly decrease to "zeroandfthe wiperwill movefdoivnwardly so that dur-ing .the f turnfthe ailerons are:'fcontroiled Il). practically-:entirely by the gyro 62. Only if aperisistenthank yangle error develops at selsyn 24 will --an veffectivecorrective signal get through to the gyro 62. `As hereinbefore statedthe same expedient may advantageously be used on the pitch axisthoughnotherein illustrated.

Up to this pointthe system described and illustrated has been one inwhich craft rate of turn has been predetermined and Proper controlsignals for` achievinga proper craft bank angle for the desired rate ofturn were determined by the system. However, .the instant invention isnot limited to such-systems .but also has equal application tosystemswhereinthe craft bank angle isv predetermined and .proper controlmoments of the craftprolductive of vaproper. rate of turn for thepredeterininedA bank angleare determined by the system..A'system'imeetingthis requirement is illustratedin Figf vwherein acontrol knob I 5|, ofthe type thatmay'be moved in any directionisprovided With'selsyn |52 responsive to movementof knobv I5 Lon` thepitchaxis, and with selsyn |53, responsive' to movement of knob |5| onthe roll axis. fBy displacing knob |5|, craft angle of` bank may bepredetermined, or alternatively or additionally, craft angle ofelevation may be predetermined. Selsyn |53, located on the craftrollfaxisand responsive to predetermined craftangle of bank, isoperatively associated with Selsyn |55 through the lines |54. Selsyn |55is positioned on the roll axis of a vertical gyro' |55 andupon receivingsignals from the Selsyn |53, will'cause a corresponding'output signal toappear between the lines |5|,`and |53 if the position of the gyro |56inroll is in disagreement with the predetermined angle of bank. Thusly,upon the occurrence Vof a Ldisagreement between selsyns E53 and |55, asignal will appear along the lines |51 and |53` which will be inproportion to that disagreement. When this signal is applied to theprecessiontorquer|59,"wh-ichl is located on the torque'ffvgyrov |6|, aprecession of gyrov 55| will be eiected thereby causing theselsynpick-off |62 to transmit 1a control signal to aileron controldevices, hereinafter described. The aileron control devices havingreceiveda control signal will thereupon provide the craft with an angleof bank that is in-accordance with the predetermined `angle of bankas-set in control knob |5i. Thereupon the selsyn |53 also located on thecraft roll axis being energized by the alternating current `source |54will transmit a signal into the computerfi-which 'will be lproportionalto the craft bank angle. v'The details of this computer willbefdescribed later but it is productive of an output across points |55and i6? that is proportional to-a rate of turn which would be proper forthe predetermined bank angle, or more specifically the computed'rateofturn l would be equal to ,g tan 0B V cos @E Having provided means forsupplying a signal across points |58 and |69, which signal would be inaccordance with computed craft rate of turn for a predetermined craftbank angle, the remainder of the system is similar in all major respectsto the system set forth in Fig. 1. A signal responsive to the computedrate of turn is applied to `a cosine selsyn |1| located on the roll axisof vertical gyro |56 and having its output connected by lines |12 and|13, to a cosine selsyn |15 which is located on the pitch axis of thevertical gyro |55. By this arrangement a signal appearing across lines|15 and |16 is produced which is proportional to (o cos B cos 0E).Similarly, a sine selsyn |11, located on the roll axis of the verticalgyro |56, is energized by the rate of turn signal (fr) and is therebyproductive of an output appearing along lines |18 and |19 which isproportional to the rate of turn times the sine of the craft bank angle.This signal is fed into the cosine selsyn |8| located on the pitch axisof the vertical gyro |56 thereby enabling the selsyn |8| to have anoutput along lines |82 and |83 which is proportional to (o sin 0B cos0E). rllliis signal is applied to the precession torquer |94 located onthe gyro |85 which upon precession causes an output signal to beproduced in the selsyn pick-off |85 which in turn is transmitted to, inthis instance, elevator control devices, hereinafter described.

A similar precession torquer |81 is provided on the gyro |88 forreceiving signals transmitted by the lines |15 and |16 and therebycauses, upon precession of the gyro |88, a control signal to appear inthe selsyn |89 which in turn is transmitted to rubber control devices,hereinafter described.

A third selsyn |9| of the sinusoidal type is located on the pitch axis0f the vertical gyro |56 and upon receiving signals responsive to therate of turn (r) by lines |68 and |69 produces an output signalproportional to the craft rate of turn times the sine of the angle ofelevation, which signal is applied to the precession torquer |59 of theaileron gyro |61.

G-yros |6|, |85 and |88 are also provided with pick-off and torquemeans, not shown, for maintaining the spin axis at right angles to theplane f the gimbal members, in a known manner.

As the control knob |5| is moved backwardly or forwardly, the selsyn |52being energized by the alternating current source |64 will cause asignal to be transmitted along the conductors |95 Whenever adisagreement exists between the position of the selsyn |52 and a selsyn|92 which is located on the pitch axis of the Vertical gyro |55. In theevent a signal is produced as an output from selsyn |92, this signalwill be responsive to predetermined craft angle of elevation and willIbe transmitted by lines 94, |95 to the cosine selsyn |93. Inasmuch asthe cosine selsyn |93 is located on the roll axis of the vertical gyro|56, the output from selsyn |93 will be proportional to the craft angleof elevation times the cosine of the craft bank angle, and this outputwill appear across lines |96 and |91 and will be transmitted thereby tothe elevator gyro precession torquer |84.

Sine selsyn |98 similarly modifies the signal to the rudder gyroprecession torquer |81 by supplying thereto a signal, transmitted bylines |99 and 29|, that is proportional to the craft angle of elevationtimes the sine of the craft bank angle. In this manner, through controlof the knob |5| a predetermined bank angle will be accompanied by acomputed rate of turn that will be proper for that particular bank angleand furthermore, if desired, a predetermined craft angle of elevationmay also be provided whereupon the system of Fig. 3 will produce propercontrol signals for achieving proper control moments of the craft thatwill be productive of a desired maneuver. A flux valve with pickoff anddifferential selsyn similar to that illustrated in Fig. l may beincorporated into the system of Fig. 3 to provide a heading reference.

The aileron, elevator and ruder control devices hereinafter referred tomay each comprise a conventional servomotor system as illustrated inFig. 3. For example, the signal from selsyn |52 may be transmitted overleads 399 to a conventional amplifier 36|, the output of which controlsthe direction and rate of rotation of a servomotor 392. Motor 392 ismechanically connected to operate the ailerons 393 in a conventionalmanner and a signal generator 955 is also driven by motor 362 to providea signal proportional to the output displacement of the motor which isfed back along leads 395 in degenerative fashion to the amplier 35|. Inthis manner, the displacement output of the servomotor is proportionalto the magnitude of the input signal. Furthermore, the servomotor systemis of a phase sensitive nature such that the direction of operation ofthe motor will depend upon the phase of the signal derived from theselsyn |62. Similarly, the signal from selsyn |86 is supplied to leads400 in controlling relation to amplifier 59| which controls servomotor492 which in turn operates the elevators 593. The displacementrepeat-back signal is derived from signal generator 494 and is fed backto the amplifier over leads 405. The rudder is also driven in accordancewith the signal output derived from selsyn |89 through a similarservomotor system. Briefly, this comprises the leads 592 which connectselsyn |89 with amplifier 59|, the output of amplier 56| controllingmotor 562 which drives rudder 503. Signal generator 595 provides arepeat-back signal which is supplied along leads 505 in degenerativefashion to the amplier 50|. It will be noted that the servomotor systemsherein disclosed are exemplary in character and are intended to beconventional such that a phase sensitive operation thereof may beobtained in any well known manner.

Fig. 4 illustrates in detail the component parts of the computer |65that appears in the system of Fig. 3. As in the case of the computer |6,described in detail in relation to Fig. 2, certain parts of the computer|65 are illustrated in Fig. 4 as being enclosed within the computeritself. More particularly, the vertical gyro |56 is illustrated forreasons of simplicity as being a part of the computer.

Referring now to Fig. 4, the vertical gyro |56' is provided with anoffset wiper arm 2&2 which is adapted to travel on the winding of anautotransformer 2|3, which autotransformer is provided with analternating current source 2m applied to points 2|5 and 2|6. Upon motionof the craft about the pitch axis, wiper 2|2 will be displaced along theautotransformer winding 2 i3 and will be productive of an output signalon lines 2|1 and 2|8 in an amount proportional to the secant of theangle of elevation. By applying this signal to the points 2|9 and 22| ofa second autotransformer, which is equipped with a wiper 222 that is inturn attached by means tof .the shaft :223 t tothe airspeed.:device1224, .fa-n output. signal may :be obtained across 1lines .225and'226 which would be substantiallyin propor- .tionto the secantnf thecraft, angle v,of elevation divided by the craftvelocity;Yor,--asthesecant is theV reciprocal-ofI the cosine` the signal.appearing across lpoints Y225 and 22,6 :Willbe in :propor- .tiongto thereciprocal of the craft'velocity times .the cosineyof thecraft.angle-ofelevation.

AAs it isfdesiredtoobtain thetangential function of :this reciprocaliquantity, ,1a third autovtransformer 221,-is-.fprovidedand is;suppliedwith arg-signal proportional 'to.,t11is reciprocal function atpoints 228and 2219. Wiper jarmf23| isattached by ,a shaft-.23.2 to the verticalgyro |56 in any suitable 4mar-mer, .though not ,-.shcwn, .whereby arm23| vvill-begdisplaced from the vertical in i accordance with the lcraftbank angle. By obtaining an outputffrom,thegcentertapped line 233 andtheWiper arm .'23|, a --computed voutput will begproduced .that Willqbe.proportional to the tangent of thecraftbankzanglefdivided by. the,product of the 1craft rate .of turn and the cosine'of thefcraft, angleofelevation. 'Ihissignal would be applied insFig. 3;to;points IE6-and |57and thereby complete the detail .of the computer unit |65.

W'hile the apparatus described lin relation to allthe figures havebeenshown yfasfadapted to ,supply Aproper signa-1s ,to angular kmovement.responsiveinertial means ofV the :torquedvgyro type, the sameprinciplesmaybeemployed Ain systems using angular acceleration measuring'.devices. -Thusly,-Fig..5 illustrates ayaw-accelerometer 25| which maybe provided inlieu of. forinstanca the torquedggyro |88 ofFig. 3.Thesignal that is proportional to the .rate of turn 1.times the cosineof-thefangle of bank timesthe cosine of the. angle of elevation isreceived, in y this` case,

yalongthe lines 52 and `253Mand is Aapplied to the amplierliandalsofrectified therein. This amplified and rectified signal fis 4thensupplied vrtothe differentiating network `255.Whereupon theresultingsignal from the differentiatingnetwork is yapplied to .produceabias ,torque on the.Y coil y 256 thereby causing a displacement of therotor 251; located within theeldof coil-2 56 `and theren `byproductiveof-.an angular displacement of the .accelerometer .25

Upon displacement ofthefaccelerometer 25|,

a signalpick-oi device illustrated ate-2581is`provided totransmitfcontrolsignals to 1the-surface control device (the ruddercontrol device-infthis instance). .A calibrated spring 2 5Smaintains theaccelerorneterfi ina neutralposition during the yabsence ofcontrolsignals -andservesto 'restrain Vaccelerometer movement'in amanner yto provide va displacement responsive .td-accelerationwhen asignal is supplied thereto. ThiS-Samearrangement may bealternatively-.used in thesar-ne--coniiguration on thejpitch axiscontrols, or,'more particularltnin control 4-of the elevator .surfacecontrols. However, if incorporated to -supply signals-to the roll axiscontrolling devices (the ailerons) adierentiatorwould. be required onlyin the'fleads'from the sine-selsyn |-S| of Fie. -3 but not in the linesf |151 Iand |58, iwhichlatter lines transmit thesignal-proporticnal to.thegpredetermined angle of bank.

What is claimedV is:

l. An automaticightfcontrol apparatus for dirigible craft havingsignalpresponsive idevices for supplying controlmoments-theretoffsaidfapparatus comprising means for producingicontrolsignals dependent upon craft .deviatio11;f;rom aa predeterminedattitude, inertial angular-movement-responsive means for producingcontrol .signals Vdependent on angular movement about theprimarygcraftaxes, means for modifying, said produced controlsignals to .effectpredetermined craft angle of elevation, meansvfor further modifyingfsaidproduced :control signals inaccordance with measures of'craft rate ofturn `and craftv bank angle, said last mentioned means including'acomputing mechanism for vdetermining one of saidmeasures from alpredetermined value ofthe other lof `said measures.

2. An automatic iiightrcontrol apparatus for 4dirigible craft havingsignal responsive vdevices for vsupplying control moments thereto, saidapparatus comprising-a threefaxis'reference device, picifoif meansforeach axis of said reference devicerforfproduc-ing control signalsresponsive to craft deviationgfrom predetermined attitude, inlertial;rnea-ns "for .producing control signals respon'sive tog-angularmovementabout the primary craft taxes, -means :for Amodifying said producedcontrol .ssignals Y-gto .effect a predetermined craft angle `ofaeievation, :means f or further modifying said produced controly signalsin accordancewith measures of f craft rate. oiY turn and craft bankangle, saidlast mentioned .means incl iding a computing mechanism :fordetermining one of said umeasures'frorni-a predetermined value of the.other of ,said-.measures .13. fAn automatic night control .apparatusfor dirigi'ble `.craft :having :signal responsive devices for supplyingcontrol-moments'thereto,;said ap- :paratus comprising means forsupplying control signals vdependent-upon craft deviations from apredetermined attitude, meansl for supplying control tsignals dependentonangular craft movefment, f'n'leansffor4 modifying said control signals.to "effect control :moments `.productive or" prede- .terininedcraf t.'angle .of elevation, means for producingftwo additional nodifyingsignals vrespec- ...tively :dependent upon -crait rate of turn and craftangle of bank, the value :of one-,of said last-imentionedmodifyingsignals vbeing manually setrin andnmeansffor `computingy thevalue of the other iin :accordance with the. set in value, land 4meansforgmodifying the operation ofsaid signal responsivefdevicesinfaccordancevwith said two .additional .f modif ying signals.

`lixlnanautoniatic night control system for a craft, means :forcoordinating craft bank angle withpredetermine'd craft rate of turnincluding aziirst"Signalfproducingmeans havingl an output .corresponding:to `a n.preldeterrnined rate of turn, .a crafteair .speed measuringdevice, a second signal p1oducing;means'having an output dependent uponcraft air speed, and computing -meanshaving-an.outputproportional to atangential functionroffthe product of the outputs from `vsaid 'rst andsecond signal producing means.

'5. `Inanautomatic flight lcontrol system for a dirig-blecraft, meansforcoordinating craft bank angle'with predetermined craft rate of turninclu'dingarst signalproducing means having an output ldependent uponthe predetermined rate of turn,. .a.'device-forfmeasuring craft ,airspeed, .a.-second signal. producingmeans havingan outputdependent. upon.said craft air. speed, .means forimeasuring-craft'angle of f elevation,a third -signal producing l.means #having an output dependent upon acosine .function `of saidcraft .angle off-elevation, andccmputing meanshaving :annum-ut dependent uponra Atangential.function of the product ofoutputs from said rst, second and third signal producing means.

6. In an automatic flight control system for a dirigible craft, thecombination of means having an output signal responsive to actual craftbank angle, means having an output signal responsive to a computed craftbank angle for a given rate of turn, and circuit means having an outputdependent upon the difference between said signals, said computing meansincluding a craft air speed measuring device, a craft angle of elevationmeasuring device, pick-off means having an output dependent upon theproduct of the rate of turn, said air speed, and a cosine function ofsaid angle of elevation, and means for determining the angle Whosetangent is proportional to said product.

7. In a turn control for a dirigible craft, a computer for producing anerror signal dependent upon disagreement between actual and computedcraft bank angle for a preselected craft rate of turn, said computercomprising rst signal producing means having an output in accordancewith predetermined rate of turn, second signal producing means having anoutput in accordance with craft air speed, third signal producing meanshaving an output in accordance With the cosine function of craft angleof elevation, means for obtaining a fourth signal proportional to theproduct of said rst, second and third signals, means for computing theangle Whose tangent is equal to said fourth signal, and means forproducing a fifth signal in accordance with actual craft bank angle.

8. In a flight control system for a dirigible craft, means for measuringcraft angle of elevation, a pick-olf for said means having an outputdependent upon a sinusoidal function of said craft angle of elevation,means having an output signal dependent upon predetermined craft rate ofturn, and computing means having a signal output proportional to theproduct of said rate of turn and said sinusoidal function of angle ofelevation.

9. In a night control system for a dirigible craft, means for producinga first output signal in accordance with predetermined craft rate ofturn, means responsive to craft angle of elevation, a pick-off on saidlast mentioned means for producing a second output signal dependent upona cosinusoidal function of said craft angle of D put signal inaccordance with a cosinusoidal function of said angle of elevation,means responsive to craft angle of bank including means for producing athird output signal in accordance with a cosinusoidal function of saidbank angle, and comp-uting means responsive to the product of saidfirst, second and third output signals.

l1. In an automatic flight control system for a dirigible craft, meansfor coordinating craft rate of turn with predetermined craft bank angleincluding a first signal producing means having an output dependent uponthe bank angle of the craft, a craft air speed measuring device, asecond signal producing means having an output 16 proportional to craftair speed, and computing means having an output responsive to atangential function of the output from said rst signal producing meansdivided by the output from said second Signal producing means.

12. In an automatic flight control system for a dirigible craft, meansfor coordinating craft rate of turn with predetermined craft bank angle,including a iirst signal producing means having an output dependent uponsaid predetermined craft bank angle, a device for measuring craft airspeed, a second signal producing means having an output dependent uponsaid craft air speed, means for measuring craft angle of elevation, athird signal producing means having an output dependent upon a cosinefunction of said craft angle of elevation, and computing means having anoutput dependent upon a tangential function of the output from saidfirst signal producing means and said function divided by the product ofoutputs from said second and third signal producing means.

13. In an automatic flight control system for a dirigible craft, thecombination of means having an output dependent upon craft bank angle,means for producing an output signal proportional to computed craft rateof turn for a predetermined craft bank angle, and circuit means fortransmitting said computed rate of turn signal to produce craft controlmoments proportional thereto, said computing means including a craft airspeed measuring device, means for producing a first signal dependent onsaid air speed measuring device, means having an output dependent uponcraft angle of elevation, means for producing a second signal dependentupon a cosine function of said craft angle of elevation, and means forproducing an output signal dependent on a tangential function of saidpredetermined craft bank angle, and divided by the product of said rstand second signals.

i4. In a flight control system for a dirigible craft, means formeasuring craft angle of elevation, a pick-off for said means having anoutput dependent upon a sinusoidal function of said craft angle ofelevation, means having an output signal dependent upon the craft bankangle, means having an output dependent upon craft rate of turn for apredetermined craft lbank angle, and computing means having an outputdependent upon the product of said craft rate of turn and saidsinusoidalfunction of craft angle of elevation.

In a flight control system for dirigible craft, means for producing anoutput in accordance with predetermined craft bank angle, means forproducing a first signal proportional to craft rate of turn as computedfrom said predetermined craft bank angle, means responsive to craftangle of elevation, a pick-off on said lastmentloned means for producinga second signal dependent upon a cosinusoidal function of said craftangle of elevation, means for producingr a third signal responsive to asinusoidal function of said craft bank angle, and computing means havingan output responsive to the product of said first, second and thirdsignals.

16. In a flight control system for a dirigible craft, means forproducing an output dependent upon a predetermined craft bank angle,means for producing a first signal proportional to craft rate of turn ascomputed from said predetermined craft bank angle, means responsive tocraft angle of elevation including a pick-olf for producing a secondsignal proportional to a coaces-,264

sinusoidal' function of said angle o'f elevation,

means for producing a third signal proportional to' a cosinusoidalfunction of craft angle of bank, and computing means responsive to theproduct of saidrst, second, and third signals.

17. InanY automatic flight control systeml for a dirigible craft, meansfor supplying craft control'- movements comprising means for computingthe centrifugal acceleration active on said craft including means havinganoutput responsive to? craft air speed and means'- having anoutputresponsive to craft rate of' turn, meansA for providing anoutputproportionalv t'oa cosinusoidal function of craft angle of elevation,and a con:- puting means for producing a control signal responsve to theproduct of all of said outputs.

18.. Flight control apparatus for craft' and missiles comprisinginertial signal producing devices,- one of whichproduces al controlsignal responsive to angular movement of the craft about. each of theprimary craft axes to normally' maintain straight and level flight,settable means operatively associated w-ith each of the said inertial'signal devices to alter said control signals to cause turn about anydesiredv axis, an attitude reference stabilized' with respect to theearth, and resolving means associated withV said attitude reference forapportioning said altered signals. between the several inertial devicesdepending on the tilt of the craft axes whereby the desired rate of turnaboutl the desi-red axis is secured regardless of the crafts attitude.

19. Flightlcontrol apparatus for crafts and missiles comprising inertialsignal producing devices responsive to angular movement of the craftabout.' each of the primary craft axes to normally maintain straightvand level flight, settabl'e means operatively associated withv each ofsaid` inertial devices to alter said signals to cause craft turnraboutany desired axis', an attitude reference stabilized' with respectv tothe earth, and' resolving means associated with said attitude referencefor apportioningsaid altered signals between the several inertialdevices dependingv on` thel tilt of the craft axes in a sense to renderthe net control signals zerowheny the craft isv executing the. maneuverdemanded by the said settable means.

20. In an automatic steering apparatus, an inertial device having meansfor producing a signal responsive to yaw, a magnetic compass devicehaving a pick-off for producing a signal responsive to headingdeviations, normally' in'- effective follow-up means for zeroing saidpickoif, steering means normally responsive to the combination ofsignals from said devices, a turn control including means for biasingsaidv yaw responsive signal to produce yaw., and means brought intoaction by said turn control causing said compass signal to be divertedfrom said steering means and applied to cause said followupmeans to zerosaid compass pick-off.

2l. In an automatic stabilizing means for aircraft, a free gyroscopehaving freedom aboutthe roll axis of the craft, a second free gyroscopehaving freedom about the pitch axis, servo means controlled from bothgyroscopes for maintaining level ilight, and means for preventingwandering of said gyroscopes about said roll and pitch axes respectivelyincluding a gyro vertical, and means responsive to tilt of the craftwith respect to said gyro vertical for processing said roll and pitchgyroscopes respectively back to ther normal attitude at a limitedmaximum rate of procession.

22. In an automatic stabilizing means for aircraft, free gyroscope meanshaving signal producing pick-offs responsive to craft roll and craftpitch, servo means controlled from said signals for maintaining levelflight, and means for preventing wandering of said gyroscope means aboutsaid` roll and pitch axes respectively including a gyro vertical, andmeans responsive to tilt of the. craft with respect to said gyroVertical for processing said free gyroscope means backto a normalattitude at a limited maximum rate of precession.

23. In an automatic stabilizing means for aircraft, an inertial deviceresponsive to movement about the roll axis of the craft, a secondinertial device responsive to movement about the pitch axis of thecraft, servo means controlled from both inertial devices for maintaininglevel flight and means for preventing deviations of said inertial deviceabout said roll and pitch axesy respectively, including a verticalreference and means responsive to tilt of the craft with respect theretofor slowly re-positioning said roll and pitch inertial devicerespectively back to their normal position.

24. In an automatic stabilizing means for aircraft, an inertial deviceresponsive to movement about the roll axis of the craft, a secondinertial device responsive to movement about the pitch axis of thecraft, a third inertial device responsive to movement about the yaw axisof the craft, servo means controlled from each of theY said inertialdevices for maintaining straight and level night, and means forpreventing deviations of said inertial devices about said primary axesrespectively, including a vertical reference and an azimuth referencedevice, and means responsive to craft angular error with respect to saidvertical and azimuth reference devices, respectively, for slowlyre-positioning said in ertial devices respectively back to their normalposition.

25` In flight control apparatus for aircraft, inertial means responsiveto angular movements of the aircraft with respect to space about atleast the roll and pitch axes and arranged to produce signals onoccurrence of' such movements,y servo means operated by the signals andadaptedv to apply corrective control forces to the airplane tocounteract such movements, means denning a reference with respect to theearth, signal producing means responsive to relative tilt of theaircraft and reference means, a signal channel coupling the tilt signalproducing means and the inertial device signal producing means wherebythe tilt signal can overpower the inertial device signal, means in saidchannel operativey onl decay of the tilt signal for limiting the tiltsignal channel sensitivity to a low value, and means operated by thetiltsignal for slowly raising theV limit in the presence of persistenttilt signal, ywhereby short-period angular movements of the aircraft invspace are corrected mainly by the inertial means and persistent tilt ofthe aircraft relative to the earth is corrected by the earth. referencemeans.

26; Flight control apparatus for' aircraft comprising aircraft controlmeans for producing an.- gular movements of said craft about an axisthereof, a rst means sensitive to a rate of angular movement of saidcraft about said axis for controlling said aircraft control means torestore said craft to its initial position following relatively shortperiod angular deviations thereof, means denning a space axis coincidentWith said craft axis, a second means associated With said spaceaxis-defining means and responsive to angular deviations of said craftabout said space axis for controlling said aircraft control means inaccordance with relatively long period angular deviations of said craftto restore said craft to its initial position relative to saidspaceaxis-deiining means, and means for normally providing a relativelysmall degree of control by said second means over Said aircraft controlmeans but for increasing the degree of control of said second means oversaid aircraft control means in accordance With the time interval duringwhich an angular deviation of said aircraft about said space axis maypersist.

27. Flight control apparatus for aircraft comprising aircraft controlmeans for producing angular movements of said craft about mutuallyperpendicular axes thereof, rate gyros respectively responsive toangular rates of movement of said craft about said axes, means includingiirst signal pick-offs associated with said rate gyros for controllingsaid aircraft control means respectively to restore said craft to itsinitial attitude following relatively short period angular deviations ofsaid craft about said axes, means including a gyro vertical for definingspace axes coincident With'said craft axes, means including secondsignal pick-ons associated with said gyro vertical for respectivelycontrolling said aircraft u control means in accordance with relativelylong period angular deviations of said craft about said axes to restoresaid craft to its initial attitude relative to said space-axes definingmeans, and means for normally providing a relatively small signal fromsaid second signal pick-offs to said aircraft control means respectivelybut for ncreasing the signal supplied from said second signal pick-offsto said aircraft control means as a function of the time of duration ofthe signal from said second pick-offs, respectively.

28. Flight control apparatus for aircraft comprising aircraft controlmeans for producing angular movements of said craft about an axisthereof, a rate gyro sensitive to angular rates 0f movement of saidcraft about said axis, said rate gyro including a torquer and a firstsignal pickoff, means responsive to the Output of said first signalpick-off for controlling said aircraft control means to restore saidcraft to its initial position following relatively short period angulardcviations thereof about said axis, means defining a space axiscoincident with said craft axis ncluding a second signal pick-off fordetecting angular movement of said craft about said space axis, meansfor controlling the torquer of said rate gyro in accordance With thesignal developed in said second pick-off whereby to control saidaircraft control means in accordance with relatively long period angulardeviations of said craft in a manner to restore said craft to itsinitial position relative to said space axis, and means for normallysupplying a relatively small signal from said second pick-off to thetorquer of Said rate gyro but for increasing the signal so supplied inaccordance with the magnitude and persistence time of the signal outputof said second Sgnal pick-olf.

29. In a flight control system for aircraft, means dening a pitchattitude reference for said craft about its pitch axis, means defining asecond attitude reference about a second of the crafts axes, meansresponsive to said second attitude reference for controlling theattitude of said craft about said second axis, and means operativelyassociated With said pitch reference-dening means for modifying theoperation of said attitude controlling means in accordance with theangular displacements of said craft about the crafts pitch axis.

30. In a flight control system for aircraft, means defining a pitchattitude reference for said craft about its pitch axis,signal-responsive means for controlling movements of the craft about asecond of the crafts axes, a signal producing means connected to supplysignals to said signal-responsive means, and means operativelyassociated with said pitch reference and connected in circuit with saidsignal-producing means for varying the signal supplied to saidsignal-responsive means in accordance with angular displacements of saidcraft about its pitch axis.

31. A flight control system of the character recited in claim 29 inwhich the second crafts axis is its roll axis.

32. A night control system of the character recited in claim 29 in whichthe second crafts axis is its azimuth axis.

33. In a ight control system for aircraft, means dening a pitch attitudereference for said craft about its pitchaxis, signal-responsive meansfor controlling movements of the craft about a second of the craftsaxes, a signal producing means connected to supply signals to saidsignal-responsive means, and means operatively associated With saidpitch reference-defining means and connected in circuit with saidsignal-producing means for varying the signal supplied to saidsignal-responsive means as a function of the angular displacement of thecraft about its pitch axis.

34. 1n a flight control system for aircraft, means defining a pitchattitude reference for said craft about its pitch axis, rudder controland aileron control means for controlling movements of said craft inazimuth, and means for modifying the operation of both said ruddercontrol and aileron control means as cosine and sine functions,respectively, of the, pitch angle of said craft.

JOHN M. SLATER. WALTER WRIGLEY.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 2,066,194 Bates Dec. 29, 1936 2,115,498 Rieper Apr. 26, 19382,137,974 Fischel Nov. 22, 1938 2,190,390 Thiry Feb. 13,1940 2,371,388Glenny Mar. 13, 1945 2,439,750 Nisbet et al. Apr. 13, 1948 2,464,629Young Mar. 15, 1949

